Hermeus is testing a turbine engine for hypersonic reusable aircraft

Hermeus Corp. said last week that it had demonstrated the transition of a turbojet engine to a ramjet engine Chimera turbine combined cycle engine (TBCC) – a cross between a turbojet and a ramjet engine – to allow reusable hypersonic aircraft to take off from conventional runways.

“This is one of the most important technological feats to make operational hypersonic flight a reality,” Hermus said. “The cost and speed with which the Hermeus team achieved this milestone is remarkable. Hermeus designed, built and tested the Chimera in 21 months at a cost of $18 million.”

Hermus said it tested the Chimera at the Notre Dame Turbomachinery Laboratory, which supplies heated air to simulate high Mach temperatures and pressures.

“At low speeds, the Chimera is in turbojet mode — just like any jet aircraft,” Hermeus said. “But as the temperature and velocity of the incoming air increases, turbojets reach their performance limits. This occurs at Mach 2. The Chimera has a pre-cooler that lowers the temperature of the air entering the turbojet engine. This allows Hermeus to squeeze a bit more performance out of the turbojet before switching to ramjet. Around Mach 3, the Chimera begins to bypass the incoming air around the turbojet engine, and the ramjet takes over completely. “

In August last year, the US Air Force announced the awarding of A A $60 million contract to Georgia’s Hermeus to accelerate the commercial development of hypersonic aircraft and propulsion systems (Defense DailyAugust 5, 2021).

The Air Force Lifecycle Management Center’s (AFLCMC) Presidential and Executive Airlift Directorate, the Air Force Research Laboratory and venture capital funded the contract, which is part of a broader effort — the Vector Initiative — to promote high-speed passenger transportation and potentially advance Air Force technology. for high command transport; air mobility; intelligence, surveillance and reconnaissance; and other missions.

Hermeus said it plans to build its first hypersonic Quarterhorse drone and start flight testing it late next year. Hermeus is also developing the Darkhorse, an unmanned aircraft that can sustain hypersonic flight, and the Halcyon, which is intended to be a Mach 5 commercial passenger aircraft.

“The contract establishes a number of goals for Hermeus to be met within three years,” AFLCMC said last year, including increasing understanding of enabling technologies and mission capabilities for reusable hypersonic aircraft; scaling and flight testing of a reusable hypersonic propulsion system; the design, construction and testing of three Hermeus Quarterhorse concept aircraft; providing payload integration guidance for future hypersonic flight tests with Quarterhorse; and providing Wargaming data for use in Air Force strategic analysis tools.

After the three-year contract with Hermeus, the Air Force plans to evaluate the company’s progress, the maturity of hypersonics and the alignment of Hermeus’ efforts with service priorities.

In May, RTX Ventures, a capital investment group led by Raytheon Technologies [RTX]said it did a strategic investment at Hermeus for the development of commercial and military hypersonic aircraft (Defense DailyMay 12).

Ramjets, which work best between Mach 3 and 5, mix compressed air with ignited fuel to create thrust.

“The Hermeus TBCC engine is unique in the field of hypersonics,” the company said. “Most hypersonic platforms are equipped with a rocket engine. But this approach makes reusability much more difficult and inherently more dangerous for passenger flight. By creating a full-range, air-breathing hypersonic engine that does not require a rocket for acceleration, Hermeus is creating the foundation for operational hypersonic flight – meaning an aircraft that can be quickly reused.”

Hermeus compared its Quarterhorse, which should have a top speed of Mach 5 and a cruising altitude of 95,000 feet, with Lockheed Martin‘s [LMT] the legendary SR-71 Blackbird, which first flew in 1964 and had a top speed of over Mach 3 and a cruising altitude of 85,000 feet.